Timekeepers Add an Extra 'Leap' Second that Could Shut Down the Internet

It will take us a little longer to get to July than usual, as timekeepers are officially adding an extra second to today, June 30, at midnight. As the Earth's rotation gradually slows down over the years, we have been forced to add an extra second on occasion in order to make up for the differences between the actual solar day and our 24-hour day.

Earth's rotation is perpetually slowing down, so the actual solar day has not been exactly 24 hours (86,400 seconds) since about 1820. In order to make up for this difference, timekeepers can add a "leap" second at the end of June or December. So tonight, at 23:59:59, we will all literally get an extra second before midnight, as the clock will read 23:59:60 for one second before switching over to 00:00:00 as usual.

This doesn't sound like a very significant change, but the trouble lies in the leap second's irregularity. For reasons unknown to the scientific community, the slowing of the Earth's rotation is not constant, so there is essentially no rhyme or reason to the addition of leap seconds. Nine seconds were inserted between 1972 and 1979, while today's leap second is only the fourth since 1999.

As a result of this irregularity, the leap second causes everything to shut down. Computing systems get confused after the leap second is inserted, because there's no way to know how many seconds passed between any two dates, and everything is generally thrown out of whack. When the last leap second was added in 2012, Reddit, Gawker, Amazon, and multiple Linux servers crashed; there were even problems with Australian airline Qantas Airways, causing delays in up to 50 flights.

As the leap second happens at atomic midnight, this Y2K-redux will happen at different times around the globe: 5pm PDT, 8pm EDT, 1am BST, and 2am CEST. Be ready.